1. Field of the Invention
The present invention relates to a chassis structure for a mid-wheel drive power wheelchair, and more particularly to one that uses a restricting rack having a slot to absorb a slight drop height of a front wheel rod, a driving unit and a rear wheel rod and to maintain a balancing of wheels.
2. Description of the Prior Art
Wheelchairs are necessity to the elderly and some disabled people for their daily life. As shown in FIG. 11, a conventional chassis structure for a mid-wheel drive power wheelchair comprises a frame A, a front wheel unit B, a driving unit C, a shock absorber unit D and a rear wheel unit E. The shock absorber unit D is pivotally connected to the frame A. The shock absorber unit D comprises a rod D1 and a block D2 at a central section thereof. The block D2 has a first end D21 and a second end D22. The block D2 is secured to the frame A. The first end D21 of the block D2 is provided with a first connecting seat D3. The first connecting seat D3 is secured to a connecting member C1 of the driving unit C. A first elastic member D4 is provided between the block D2 and the first end D21, and a second elastic member D5 is provided between the block D2 and the second end D22 for maintaining a high stability of the wheelchair and providing a shock absorbing effect.
However, if the wheelchair runs on a depression or a bump in a fast speed, the front wheel unit B, the driving unit C and the rear wheel unit E will have a differential drop height. Thus, the first elastic member D4 and the second elastic member D5 can not react in a first response and the wheelchair will have a minus vibration, which makes the rider uncomfortable. Once the vibration is too strong, the frame A may incline.